Invisible light. Otherwise known as UV. Rays are shorter than violet and longer than X-Rays thus it lies just beyond the violet end of the spectrum. Exposure to either UVA or UVB is harmful to both the eyes and skin. All standard sunglasses should provide protection and are particularly important when in snow or near water.

Inflammation of the uveal tract (iris, ciliary body and choroid) which can be sudden chronic or recurring. Often linked to rheumatoid arthritis and multiple sclerosis. Symptoms include light sensitivity, tearing, redness, blurred vision and pain. Can often be misdiagnosed.